1. Field of the Invention
The present invention relates to a message processing method applied to a mobile communication system, and more particularly, to a method for processing a security setup control message.
2. Description of the Related Art
A universal mobile telecommunications system (UMTS) is a third generation mobile communication system that has evolved from a standard known as Global System for Mobile communications (GSM). This standard is a European standard which aims to provide an improved mobile communication service based on a GSM core network and wideband code division multiple access (W-CDMA) technology.
FIG. 1 shows a network structure of a general UMTS. As shown in FIG. 1, the UMTS includes user equipment (UE) or a terminal 100 such as a mobile station or a subscriber unit, a UMTS terrestrial radio access network (UTRAN) 200, and a core network (CN) 300. The UTRAN 200 includes one or more radio network sub-systems (RNS). Each RNS includes a radio network control (RNC) and at least one Node B managed by the RNC.
Each Node B receives information sent by the physical layer of a terminal 100 through an uplink and transmits data to a terminal through a downlink. Each Node B operates as an access point of the UTRAN 200 for terminal 100.
Each RNC performs functions which include assigning and managing radio resources and operates as an access point with respect to the core network 300. A primary function of the UTRAN 200 is constructing and maintaining a radio access bearer (RAB) for a call connection between the terminal 100 and the core network 300. The core network 300 applies end-to-end quality of service (QoS) requirements to the RAB and the RAB supports QoS requirements set up by the core network. Accordingly, the UTRAN 200 can satisfy the end-to-end QoS requirements by constructing and maintaining the RAB.
The RAB service is divided into an lu bearer service and a radio bearer service. The lu bearer service handles reliable user data transmission between boundary nodes of the UTRAN 200 and the core network 300, while the radio bearer service handles reliable user data transmission between the terminal 100 and UTRAN 200.
FIG. 2 illustrates a radio protocol between the terminal 100 and the UTRAN 200 on the basis of the 3GPP wireless access network standards. The radio protocol is vertically formed of a physical layer, a data link layer and a network layer, and is horizontally divided into a user plane for transmitting data information and a control plane for transmitting a control signal.
The user plane is a region to which user traffic information, such as voice or an IP packet, is transmitted. The control plane is a region to which control information, such as that related to interface of a network or maintenance and management of a call, is transmitted. In FIG. 2, protocol layers can be divided into a first layer (L1), a second layer (L2) and a third layer (L3) based on three lower layers of an open system interconnection (OSI) standard model well known in communication systems.
The first layer (L1) or physical (PHY) layer provides information transfer service to the upper layer by using various radio transfer techniques. The PHY layer is connected to the media access control (MAC) layer through a transport channel, and data is transferred between the MAC layer and the PHY layer through the transport channel. The MAC layer provides a re-allocation service of the MAC parameters for allocation and re-allocation of radio resources.
The MAC layer is connected to the radio link control (RLC) layer through a logical channel, and various logical channels are provided according to the type of information transmitted. In general, when information of the control plane is transmitted, a control channel is used and when information of the user plane is transmitted, a traffic channel is used.
The MAC layer is classified into a MAC-b sublayer, a MAC-d sublayer and a MAC-c/sh sublayer according to types of managed transport channels. The MAC-b sublayer manages a broadcast channel (BCH) handling broadcast of system information. The MAC-c/sh sublayer manages a shared transport channel such as a forward access channel (FACH), downlink shared channel (DSCH), or the like which is shared with other terminals 100.
In the UTRAN 200, the MAC-c/sh sublayer is positioned at a control RNC (CRNC) and manages channels shared by every terminal 100 in a cell, so that one MAC-c/sh sublayer exists in each cell. The MAC-d sublayer manages a Dedicated Channel (DCH) which is a dedicated transport channel for a specific terminal 100. Accordingly, the MAC-d sublayer is positioned at a serving RNC (SRNC) managing a corresponding terminal 100, and one MAC-d sublayer also exists at each terminal.
The RLC layer supports reliable data transmission and may perform segmentation and concatenation of an RLC service data unit (SDU) from a higher layer. The RLC SDU transferred from a higher layer is adjusted in size according to throughput capacity at the RLC layer, header information is added, and the data transferred in the form of a protocol data unit (PDU) to the MAC layer. The RLC layer includes an RLC buffer for storing the RLC SDU or the RLC PDU from a higher layer.
A broadcast/multicast control (BMC) layer schedules a cell broadcast message (CB) transferred from the core network 300 and broadcasts the CB to a terminal 100 positioned in one or more specific cells. At the UTRAN 200, the CB message transferred from the upper layer is combined with information, such as a message ID, a serial number or a coding scheme. The resulting message is transferred in the form of a BMC message to the RLC layer and to the MAC layer through a common traffic channel (CTCH), which is a logical channel. The CTCH is mapped to a forward access channel (FACH), a transport channel, and a secondary common control physical channel (S-CCPCH), which is a physical channel.
A packet data convergence protocol (PDCP) layer is an upper layer of the RLC layer which allows data to be transmitted effectively on a radio interface with a relatively small bandwidth through a network protocol such as the IPv4 or the IPv6. The PDCP layer reduces unnecessary control information, a function called header compression. Toward this end, RFC2507 and RFC3095, which are robust header compression (ROHC) techniques defined by an Internet standardization group such as an Internet engineering task force (IETF), may be used. In these methods, only the information required for the header part of data, or control information, is transmitted. Therefore, the amount of data transmitted may be reduced.
The radio resource control (RRC) layer positioned in the lowest portion of the third layer (L3) is defined only in the control plane and controls the logical channels, the transport channels, and the physical channels with regard to setup, reconfiguration, and release of the radio bearers (RB). Upon request from higher layers, an RRC layer controls transport and physical channels to perform the establishment, reconfiguration, and release of RB. The RB signify a service provided by the second layer (L2) for data transmission between the terminal 100 and UTRAN 200. Setting up the RB includes stipulating the characteristics of a protocol layer and a channel, which are required for providing a specific service, and setting the respective detailed parameters and operation methods.
Various channels for receiving and transmitting data are defined for use between a terminal 100 and UTRAN 200. Data is sent and received between the PHY layer of a terminal 100 and that of the UTRAN 200 using a physical channel. In addition to the physical channel, data transport paths between the protocol layers are defined as transport and logical channels in the radio access network of the UMTS. The logical channels are provided for data exchange between the RLC and MAC layer, while the transport channels are provided for data exchange between the MAC layer and PHY layer. Mapping between transport channels is performed in the MAC layer, while mapping between the transport and PHY layer is performed in the PHY layer.
Various types of messages are received and transmitted between the terminal 100 and UTRAN 200. Security checks are performed to protect data contained in the messages. Security checks may include ciphering and integrity check.
Ciphering adds a specific mask, known only to the transmitting and receiving parties, to a message such that a third party not knowing the mask is unable to recognize the contents of the message. Integrity check is utilized to check whether an unauthorized third party has altered the contents of the message or whether an unauthenticated party made the transmission. Integrity check is also performed to check whether a third party intentionally changed the contents of the received message.
In the UMTS, the ciphering and the integrity check are simultaneously carried out on most messages transferred to the RRC layer and most control messages transmitted to the upper layers of the RRC layer. Ciphering is also performed on other general user data. Integrity check can be carried out in the RRC layer.
To determine if the contents of a message were changed by a third party between the transmitting and receiving parties or to filter a message transmitted from an unauthenticated transmitting party, the receiving party performs integrity check on the received message. The received message is processed or discarded according to the results of the integrity check.
One of the received messages may be a security setup control message. For communication between a terminal 100 and the network, for example the UTRAN 200, a security setup control message is used for initiating secure message transmission. Furthermore, a security setup control message may be used for controlling security variables that are used for the connection over which the secure messages are transmitted.
Referring to FIG. 3, a conventional method (S10) for processing a general message is illustrated. When a terminal 100 receives a general message (S11), an integrity check is performed (S12). The integrity check may utilize security variables which are set based on information contained in security setup control messages.
In accordance with the result of the integrity check, the general message is either processed or discarded. If the general message passes the integrity check, it is processed (S13). If the general message fails the integrity check, it is discarded (S14).
Information related to controlling the security variables, which may be contained in a security setup control message, is called security-related environment variables or security setup information. Since security setup information contained in a security setup control message is also vulnerable to alteration by an unauthenticated third party or may be transmitted by an unauthenticated transmitting party, the security setup information may also be unreliable.
Therefore, there is a need for an apparatus and method of processing a security setup control message such that future general messages may still be exchanged between the receiving and transmitting parties when a security setup control message is deemed unreliable and discarded due to a failed integrity check. The present invention addresses these and other needs.